FTP User With Access to Multiple Sites?

Is at all possible to have a single FTP user with access to multiple web site directories?

I have ISPConfig 3 on CentOS 6.2 and followed the Perfect Guide. Everything is working well from what I can tell. I've added a client and as that client I added a web site. I also created a user to be able to upload files to the server. This all worked fine.

I've now created a second site and expected that the same client user would be able to access the files for this web site, but found that it cannot. When viewing the options for the ftp user, I see that it is tied to a particular site. I tried changing the root directory for the user to

/var/www/clients/client1

but ISPConfig complains that the "Directory not inside of web root directory."